ERROR opening https://cactus.nci.nih.gov/chemical/structure/NH4%20.N-%28N%20%28%3DO%29O-%29N%20%28%3DO%29O-/file?format=sdf&get3d=True  -- NH4%20.N-%28N%20%28%3DO%29O-%29N%20%28%3DO%29O- could not be loaded.